Initial database schema

Diesel is used for schema migrations (written in raw SQL; targetting
PostgreSQL at the moment) and conversions between SQL and Rust
datatypes.

.github/workflows/tests.yml

@@ -48,6 +48,14 @@ jobs:
           toolchain: ${{ matrix.rust-version }}
           override: true
 
+      - name: Install libpq (Windows)
+        if: matrix.os == 'windows-latest'
+        shell: bash
+        run: |
+          choco install postgresql12 --force --params '/Password:root'
+          echo '::add-path::C:\Program Files\PostgreSQL\12\bin'
+          echo '::add-path::C:\Program Files\PostgreSQL\12\lib'
+
       - uses: actions-rs/cargo@v1
         with:
           command: test

Cargo.toml

@@ -16,5 +16,7 @@ categories = [
 publish = false
 
 [dependencies]
+chrono = "0.4.13"
+diesel = { version = "1.4.5", features = ["postgres"] }
 rocket = "0.4.5"
 rocket_contrib = {version = "0.4.5", features = ["json"]}

diesel.toml

@@ -0,0 +1,8 @@
+# For documentation on how to configure this file,
+# see diesel.rs/guides/configuring-diesel-cli
+
+[print_schema]
+file = "src/storage/sql/schema.rs"
+
+[migrations_directory]
+dir = "src/storage/sql/migrations"

src/main.rs

@@ -5,13 +5,16 @@
 
 #![feature(proc_macro_hygiene, decl_macro)]
 
+#[macro_use]
+extern crate diesel;
 #[macro_use]
 extern crate rocket;
 #[macro_use]
 extern crate rocket_contrib;
 
 mod application;
 mod routes;
+mod storage;
 
 fn main() {
     let app = application::create_app();

src/storage/mod.rs

@@ -0,0 +1,3 @@
+// Do not fail compilation until we've started using that code
+#[allow(dead_code)]
+pub mod sql;

src/storage/sql/migrations/2020-07-25-065258_create_snippets/down.sql

@@ -0,0 +1,3 @@
+DROP TABLE tags;
+DROP TABLE changesets;
+DROP TABLE snippets;

src/storage/sql/migrations/2020-07-25-065258_create_snippets/up.sql

@@ -0,0 +1,59 @@
+CREATE TABLE snippets (
+    -- an internal autoincrementing identifier used in foreign keys.
+    -- Normally not visible publicly, except for the case when it is
+    -- used for looking legacy snippets up by id
+    id SERIAL PRIMARY KEY,
+    -- a short unique snippet identifier visible to users
+    slug VARCHAR(32) NOT NULL,
+
+    title TEXT,
+    syntax TEXT,
+    created_at TIMESTAMP WITH TIME ZONE DEFAULT NOW() NOT NULL,
+    updated_at TIMESTAMP WITH TIME ZONE DEFAULT NOW() NOT NULL,
+
+    -- slugs must be unique (this will also automatically create a unique index)
+    CONSTRAINT uq_slug UNIQUE (slug)
+);
+
+
+-- will be used for pagination; slug guarantees uniqueness of the sorting key
+CREATE INDEX snippets_created_at_slug ON snippets (created_at, slug);
+CREATE INDEX snippets_updated_at_slug ON snippets (updated_at, slug);
+
+
+CREATE TABLE changesets (
+    id SERIAL PRIMARY KEY,
+    snippet_id INTEGER NOT NULL,
+
+    -- numeric index used to determine the ordering of changesets for a given snippet
+    version INTEGER DEFAULT 0 NOT NULL,
+    content TEXT NOT NULL,
+    created_at TIMESTAMP WITH TIME ZONE DEFAULT NOW() NOT NULL,
+    updated_at TIMESTAMP WITH TIME ZONE DEFAULT NOW() NOT NULL,
+
+    -- there can be multiple changesets per snippet
+    CONSTRAINT fk_snippet FOREIGN KEY (snippet_id) REFERENCES snippets(id),
+    -- but each one is supposed to have a unique version number
+    CONSTRAINT uq_version UNIQUE (snippet_id, version),
+    -- sanity check: do not allow empty changesets
+    CONSTRAINT check_not_empty CHECK (LENGTH(content) > 0),
+    -- sanity check: version numbers are non-negative integers
+    CONSTRAINT check_non_negative_version CHECK (version >= 0)
+);
+
+
+-- tags could have been associated with snippets as M:M via an auxiliary table,
+-- but Diesel only supports child-parent associations, so let's do that instead
+CREATE TABLE tags (
+    id SERIAL PRIMARY KEY,
+    snippet_id INTEGER NOT NULL,
+
+    value TEXT NOT NULL,
+
+    -- there can be multiple tags per snippet
+    CONSTRAINT fk_snippet FOREIGN KEY (snippet_id) REFERENCES snippets(id),
+    -- do not allow to abuse the tags for storing too much data
+    CONSTRAINT check_length CHECK (LENGTH(value) < 128),
+    -- do not allow repeated tags per snippet
+    CONSTRAINT uq_snippet_tag UNIQUE (snippet_id, value)
+);

src/storage/sql/mod.rs

@@ -0,0 +1 @@
+mod schema;

src/storage/sql/schema.rs

@@ -0,0 +1,36 @@
+// @generated automatically by Diesel CLI.
+
+diesel::table! {
+    changesets (id) {
+        id -> Int4,
+        snippet_id -> Int4,
+        version -> Int4,
+        content -> Text,
+        created_at -> Timestamptz,
+        updated_at -> Timestamptz,
+    }
+}
+
+diesel::table! {
+    snippets (id) {
+        id -> Int4,
+        slug -> Varchar,
+        title -> Nullable<Text>,
+        syntax -> Nullable<Text>,
+        created_at -> Timestamptz,
+        updated_at -> Timestamptz,
+    }
+}
+
+diesel::table! {
+    tags (id) {
+        id -> Int4,
+        snippet_id -> Int4,
+        value -> Text,
+    }
+}
+
+diesel::joinable!(changesets -> snippets (snippet_id));
+diesel::joinable!(tags -> snippets (snippet_id));
+
+diesel::allow_tables_to_appear_in_same_query!(changesets, snippets, tags,);